Electron tube grid and method of making



Aug. 20, 1963 H. J. ALBRECHT 3,101,100

v ELECTRON TUBE GRID AND METHOD OFMAKING Filed Jan. 4, 1960 3 Sheets-Sheet 1 IN V EN TOR. 1 l HARuLDlALBRE BHT 2r 7% JW ArrdtA/i),

Aug. 20, 1963 H. J. ALBRECHT 3,101,100

ELECTRON TUBE GRID' AND METHOD OF MAKING Filed Jln. 4, 1960 s Sheets-Sheet 2 INVENTOR. HA1; EJLD JALBREEHT Arron 5 Aug. 20, 196.3 H. J. ALBRECHT 3,101,100

ELECTRON TUBE GRID AND METHOD OF MAKING Filed Jan. 4, 1960 v 3 Sheets-Sheet 5 0 IN VEN TOR.

I-gmw JALBRE cm United States Patent 3,101,10il ELECTRON TUBE GRID'AND METHGD OF MAKING Harold J. Albrecht, Livingston, NJL, assignor to Radio Corporation of America, a corporation of Delaware Filed .Ian. 4, 1960, Ser. No. 362

Claims. (ill. Mil-71.5)

This invention relates to wire-wound grid electrodes for electron tubes and to a method of making such grids.

One type of grid electrode for electron tubes comprises a plurality of parallel side rod wires arranged to lie in a cylindrical surface and a lateral wire wound around the array of side rods in a pluarali-ty of helical turns. The lateral wire is fixed to the side rod wires at their points of contact. The term cylindrical in describing such a grid is used herein in its broader sense, i.e., not limited to circularly cylindrical but including any surface traced by any straight line moving parallel to a fixed straight line, (We-bsters New International Dictionary, 2nd edition, G & C Merriam Company). For example, the term cylindrical grid is herein used to include elliptical, rectangular, and irregular closed cross-sectional shapes as well as open shapes such as hyperbolic and parabolic cylindrical shapes.

In such a plural-side rod, cylindrical, wire-wound grid, the lateral wire is usually of much smaller diameter than the side rod wires and usually serves as the principal electron control portion of the grid. For this reason it is often desired to fabricate the grid with the lateral wire disposed on the inner cylindrical surface on which the side rods lie. Such a construction permits a closer spacing of the lateral wire to the cathode surface thus increasing the effective control of the grid.

At least two approaches to obtain'such a grid have been attempted. In one approach a helical lateral wire was attached to the inside surfaces of the side rods. A grid so made, however, is difficult to fabricate. In another approach a lateral wire was wound around the outside of the side rods and then pressed inwardly to lie on the inner cylindrical surface on which the side rods lie. The pressing or forming operation has been performed by rolling the grid between rubber pads while it is still on the winding mandrel, or by pressing the lateral wire between the side rods in against the winding mandrel by blades or rollers.

Pressing by a rubber pad usually does not serve to adequately displace the portions of the lateral wire adjacent the side rods inwardly. Only the central portion of the lateral wire between two next adjacent side rods is efiectively moved into the plane of the side rods. To avoid this same difficulty with a blade or roller device, it is necessary that the blade or roller have a width substantially equal to the spacing between adjacent side rods. However, when a blade or roller of such width is provided, difiiculty is encountered in confining the blade or roller to the space between the side rods since the side rods themselves may be somewhat crooked or nonuniformly spaced from each other. 'In addition, with either lateral wire pressing method, if the lateral wire is not highly ductile, excessive breakage of the lateral wire is encountered due to its being stretched.

I It is therefore an object of my invention to provide a method for making an improved, wire-wound, plural side rod, cylindrical grid of the type in which the lateral wire is deformed inwardly to lie on the surface defined by the inner sides of the side rods. Specifically, it is an object of my invention to provide a method of making such a grid in which the lateral wire portions closely adjacent the side rods are sufiiciently inwardly deformed, in which the difiiculties of crooked or nonuniformly spaced side rods are either avoided or.overcome, and whereby wire breakage is avoided. p 7 According to my invention a plurality of side rods are disposed mutually parallel in a cylindrical array. I A lateral wire is wound thereuponin a number' of h'elioalturns. The lateral wire is fixed to the side rods at the mutually contacting points. The grid so fabricated is then compressed radially inward by pressing against the lateral wire portions between the side rods to displace the side rods into a smaller cylindrical array and to deform the lateral wire portions to lie contiguous with the cylindrical surface defined by the inner sides of the side rods In the drawings:

FIG. 1 is a longitudinal section of an electron tube incorporating a grid electrode made according to my invention; 7

FIG. 2 is a transverse cross section of a grid shown in FIG. 1 and made according to my invention;

1G. 3 is a transverse cross section of an unfinished grid on a winding mandrel illustrating one step in the grid forming method according to my invention;

:FIG. 4 is a transverse cross section of the unfinished grid of FIG. 3 disposed about a forming mandrel illustrating an intermediate step according to the method of my invention; v

H6. 5 is a transversecross section of a finished grid on the forming mandrel together with grid-forming means illustrating a later step in the method according to my invention;

FIG. 6 is an end elevation View of grid-forming apparatus preferred for use in practicing the method according to my invention;

FIG. 7 is a side elevation view partly in section of the apparatus of FIG. 6; and

FIG. 8 is a perspective view of an alternative grid forming apparatus which can be used in the practice of my invention.

FIG. 1 illustrates an electron tube 10 incorporating a grid electrode made according to my invention. In FIG. lthe electron tube 10 comprises an envelope including a header 12 and a shell 14. A plurality of lead-ins 16 are sealed through the header 12 and support cylindrical cathode, grid, and anode electrodes 18, 20, and 22, respectively. The electrodes 18, 20, and 22 are each fixed to a radially extending flange which is in turn mounted on the ends of various ones of the lead-ins 16. A heater coil (not shown) is connected to a pair of conductors 24 which are in turn connected to other ones of the lead ins 16.

FIG. 2 shows in transverse cross section the cylindrical grid electrode 20 made according to my invention. The grid 20 comprises 'a plurality of side rods 25 disposed in a mutually parallel, cylindrical array and a relatively fine lateral wire 26 wound therearound in a plurality of helioal turns. Portions of the lateral wire 26 between adjacent side rods 25 are deformed radially inward so that they are contiguous with the cylindrical surface defined by the inner sides of the side rods 25.

In accordance with my invention, the improved, pluralside-rod, wire-Wound, cylindrical grid 29 is fabricated in a tgvo5 mandrel step method as illustrated by FIGS. 3, 4, an

FIG. 3 illustrates an unfinished or unformed grid 20' after its having been wound on an oversize winding mandrel 28. FIG. 3 is a transverse section view of the winding mantel 28 along which the plurality of side rods 25 are disposed and around which the lateral wire 26 is wound. The diameter of the winding mandrel 28 is somewhat greater than the diameter desired for the fin-. ished grid, the purpose of which will be made apparent hereinafter by reference to FIGS. 4 and 5. While the side rod and lateral wire assembly is disposed on the winding mandrel 28, the lateral wire 26 is fixed such as by brazing, welding, or plating to the side rods at each of their points of intersecting contact.

Following fixing of the lateral Wire 26 to the side rods 25, the unformed grid 26 is removed from the winding mandrel 28 and placed around a forming mandrel 30- as shown in FIG. 4. The forming mandrel 3% is of substantially smaller diameter than that of the winding mandrel 28' when considered in relation to the size of mandrel 3% This action resulting in the finished grid 2i is illustrated at its completed stage in FIG. 5. The

forming tools 32 which may be provided, e.g., as blades or rollers, will be more fully hereinafter described. In so forming the unformed grid 2%, the side rods 25 are carried radially inward along with the lateral wire portions 34 so that they also are brought into contact with the forming mandrel 3%. Accordingly, the diameter of the finished grid 2d thus formed is somewhat less than the diameter of the unformed grid 28".

ln'contrast to the prior art practice of forming the lateral wire of such grids on the same mandrel on which they are Wound, my invention may be described as involving a radial compression of the entire grid, including both the side rods 25 and the lateral wire 26. In such a grid-compression step, each side rod 25 is actually moved closer to each of the other side rods, and any given transverse dimension of the cylindrical grid 2%? is made less than the corresponding transverse dimension of the cylindrical unformed grid 2%. Moreover, in the grid-compression step, the lateral wire portions 34 are deformed inwardly such that they lie contiguous with the cylindrical surface defined by the inner sides of the side rods 25 of the finished grid 21?.

Because of the overall compression of the grid according to my invention, a number of advantages are obtained which are nct present in prior art grid-forming methods.

Since adjacent side rods 25 are moved circumferentially closer together in the forming step according to my invention, the lateral wire portions 34 can be inwardly deformed without excessively stretching these portions. Thus, in electron tubes where it may be desired to use a relatively nonductile grid lateral wire, e.g., molybdenum, breakage which'would be encountered by prior art single-mandrel, grid-forming methods is substantially eliminated. Also, because the side rods 25 are moved circumferentially closer together in the grid-compression step, the forming tools 32 may be provided with a thickness somewhat less than the distance between side rods of the unformed grid 2i). Thus, no serious obstacle to insertion of the forming tools 32, between the side rods is created by nonuniform side rod spacing or crooked or Wavy side rods. Yet, since the forming tool compistes its compression step in a snug fit against the mu tually facing sides of adjacent side rods, it serves to deform the lateral wire portions 34 such that they extend contiguous with the cylindrical surface defined by the inner sides of the side rods substantially the complete distance from one side rod to the next. This results in a more completely contiguous disposition of the primary electron control wire 26 with the inner cylindrical surface defined by the finished grid 2%. Moreover, since at the completion of the grid-compression step the side rods are in snug contact against the sides of the forming tools 32, a straightening and uniform spacing of the side rods 25 is obtained.

The forming tools 32 may, for example, be provided either as blades or rollers. Apparatus for compressing the laterals and side rods inwardly to make a grid according to my invention includes art elongated base supporting intermediate its ends and fixed thereto a pair of brackets in which a plural roller assembly is supported. The roller assembly is provided with a central bore having spaced therearound a plurality of radially positioned inwardly biased rollers which contact the grid. An elongated carriage and support has mounted at its ends adjustable spindles or stacks for securely holding a grid and mandrel which passes through the bore of the roller assembly. The grid is compressed as the carriage is moved to face the grid and mandrel through the roller assembly.

FIGS. 6 and 7 illustrate a plural roller apparatus 46 preferred for providing the grid compression step of FIG. 5. The roller apparatus is especially suitable for fabricating a plurality of grids in a single series of grid-forming operations. The roller apparatus 40 comprises body member 42 having a bore 14 therethrough. The bore ddis of suitable size to receive therein the forming mandrel 3% on which there is disposed an axially continuous grid stick suitable for subsequently severing into a plurality of predetermined axial lengths to provide a pluraiity of grids. The body member '40 includes a plurality of slots 36 extending radially outward from the bore 44. Each slot has mounted therein a roller 43 which is supported on a yoke 5t) which contacts a set screw 52. a dial indicator 54. A spring 55 is provided for maintaining the yoke 5h and its roller 48 removed from the mandrel 3h to facilitate insertionof the mandrel and unformed grid 2h into the roller apparatus iii.

In the operation of the plural roller apparatus 46, an axially continuous stick of unformed grids 2% disposed on a forming mandrel 3d is advanced through the bore 4d of the apparatus t} so that the grid-forming rollers 4-8 press against the lateral wire portions 34 between each pair of adjacent side rods 25. Advance of the grid strip through the rollers 48 eflects the grid-cornpression step according to my invention as illustrated in KG. 5. The compressed grid stick can then be severed into individual axial lengths to provide a plurality of grids.

One arrangement which has been found suitable for holding and advancing the grid stick through the roller apparatus id is also shown in FIGS. 6 and 7. A frame member 60 has fixedly mounted between its ends a pair of opposed brackets 61 which supports the roller apparatus The frame 66 has fixed thereto a key 64 which extends longitudinally along the fname 60. A plate 65 is provided with four wheels 66 mounted in slots therein for rolling movement along the frame '60. The plate as is also provided with a longitudinal slot 67 to slidably receive the key 64 and thus maintain a desired alignment of the plate '65 in its movement along the fname as between the roller-supporting brackets 61 beneath the roller apparatus A pair of spindle supports 68 are mounted one at each end of the plate 65 and support opposed spindles 69 aligned with the roller apparatus 40. The spindles are adapted to have supported therebetween a forming mandrel Sti carrying a grid stick, which can be passed through the roller apparatus at for a grid compression operation according to my invention. Means (not shown) are provided for moving the plate 65 and the mandrel carried thereby along the frame 66 to advance the stick of unforrned grids 2% through the roller apparatus 40.

An alternative apparatus for providing the grid-compression step according to my invention is illustrated in FIG. 8. The grid-forming apparatus 70 of FIG. 8 comprises a support member '71 having a central bore therethrough and a plurality of slots extending radially outward from the bore. In this respect the support member '71 is similar to the block menrber 42 of the roller apparatus all. In each of the radially extending slots there is mounted a forming blade 72 which is adapted to be The setting of the screw 52. is indicated by advanced radially inward to provide the compression of the unforrned grid The grid-forming apparatus 70 may be mounted in an operational arrangement similar to that of the roller apparatus 40 as described with reference to FIG. 7.

Both the rollers 48 of FIGS. 6 and 7 and the blades 7 of FIG. 8 are adapted to radially compress the unformed grid 20 as illustrated by the :forming tools 32 of FIG. 5. As can be seen in FIG. 5, the tips or inner surfaces of the forming tools 32 are provided with a concavity substantially mating with that of the convexity of the forming mandrel 30. The rollers 48 and blades 72 are similarly concavely shaped.

In one actual grid electrode 20 fabricated according to the invention, the following dimensions are provided:

Mils Diameter of side rods 12 Diameter of lateral wire 26 1.5 Diameter of winding mandrel 28 250 Diameter of forming mandrel fit? 237 Thickness of forming rollers 48 49 What is claimed is:

1. The method of making a wire wound plural side rod cylindrical electron tube grid comprising the steps of laying down a plurality of side rods each extending along a cylindrical winding mandrel of given size in a uniformly spaced parallel array therearo und, winding a plurality of turns of a lateral Wire around and upon said side rods, fixing said lateral wire to said side rods at their contacting points, removing the assembly of said side rods and lateral wire from said winding mandrel and disposing it around a forming mandrel having a size less than said given size, compressing said assembly radially inward with a forming tool contacting only the portions of said lateral wire which are between. said side rods into contact with said forming mandrel so that the inwardly facing sides of portions of said lateral wire between said side rods: are contiguous with the cylindrical surface defined by the inwardly facing sides of said side rods.

2. The method of making a plurality of cylindrical Wire wound electron tube grid electrodes comprising the steps of disposing a plurality of side rod wires in a mutually parallel cylindrical array, winding a lateral wire around and upon said side rod wires in a plurality of helical turns, fixing said lateral wire to said side rod wires at their points of contachpressing inwardly against only the portions of said lateral wire which are between said side rods with a forming tool to compress the assembly of side rod wires and lateral wire radially inward so that the inner sides of said side rod Wires define the surface of a cylinder smaller than said cylindrical array and the inner sides of portions of said lateral wire between adjacent side rods lie inside the cylindrical surface delined by the outer sides of said side rods, and severing the compressed [assembly of side rods and lateral wire into a plurality of axial sections.

3. The method of making a plurality of cylindrical, wire-wound grids of given axial length comprising the steps of laying down a plurality of side rod wires each being longer than said given length to extend longitudinally along a cylindrical winding mandrel, winding a lateral wire around and upon said side rod wires in a plurality of helical turns, fixing said lateral Wire to said side rods at their contacting points, removing the assembly of said side rod wires and said lateral wire from said Winding mandrel and disposing it around a forming mandrel having a smaller size than said winding mandrel, pressing inwardl against only the portions of said lateral wire which are between said side rod wires with a forming tool to bring the inwardly facing sides thereof and of said side rods into contact with said forming mandrel, and severing the inwardly pressed assembly of side rod wires and lateral wire into a plurality of axial sections of said given length.

4. The method of making a cylindrical wire-wound grid comprising the steps of laying down a plurality of more than two side rods in substantially parallel substantially equally spaced array on a cylindrical mandrel, Winding a lateral wire around and upon said side rods in a plurality of helical turns, fixing said latenal wire to said side rods at their contacting points, removing the assembly of said side rods and said lateral wire from said Winding mandrel and depositing it around a cylindrical forming mandrel having a smaller diameter than said winding mandrel, pressing radially inwardly against portions of said lateral wire between said rods with forming tools having widths somewhat less than the distance between said side rods to bend the portions of lateral wire inwardly against the forming mandrel and laterally against the side rods and to move the side rods laterally inwardly against the forming mandreL.

5. The method of making a wire wound plural side rod cylindrical electron tube grid comprising the steps of,

laying down a plurality of side rods each extending along a cylindrical winding mandrel of given size in a uniformly spaced parallel array therearound,

winding a plurality of turns of a lateral wire around and upon said side rods,

removing the assembly of said side rods and lateral wire from said winding mandrel,

and disposing it around a forming mandrel having a size less than said given size,

compressing said assembly radially inward,

with a forming tool contacting only the portions of said lateral wire which are between said side rods into contact with said forming mandrel,

so that the inwardly facing sides of portions of said lateral Wire between said rods are contiguous with the cylindrical surface defined by the inwardly facing sides of said side rods.

References Cited in the file of this patent UNITED STATES PATENTS 1,543,033 Snelling June 23, 1925 2,155,973 Irwine et al Apr. 25, 1939 2,680,208 Gehrke June 1, 1954 2,794,934- Eisan June 4, 1957 2,906,299 Brooke Sept. 29, 1959 

1. THE METHOD OF MAKING A WIRE WOUND PLURAL SIDE ROD CYLINDRICAL ELECTRON TUBE GRID COMPRISING THE STEPS OF LAYING DOWN A PLURALITY OF SIDE RODS EACH EXTENDING ALONG A CYLINDRICAL WINDING MANDREL OF GIVEN SIZE IN A UNIFORMLY SPACED PARALLEL ARRAY THEREAROUND, WINDING A PLURALITY OF TURNS OF A LATERAL WIRE AROUND AND UPON SAID SIDE RODS, FIXING SAID LATERAL WIRE TO SAID SIDE RODS AT THEIR CONTACTING POINTS, REMOVING THE ASSEMBLY OF SAID SIDE RODS AND LATERAL WIRE FROM SAID WINDING MANDREL AND DISPOSING IT AROUND A FORMING MANDREL HAVING A SIZE LESS THAN SAID GIVEN SIZE, COMPRESSING SAID ASSEMBLY RADIALLY INWARD WITH A FORMING TOOL CONTACTING ONLY THE PORTIONS OF SAID LATERAL WIRE WHICH ARE BETWEEN SAID SIDE RODS INTO CONTACT WITH SAID FORMING MANDREL SO THAT THE INWARDLY FACING SIDES OF PORTIONS OF SAID LATERAL WIRE BETWEEN SAID SIDE RODS ARE CONTIGUOUS WITH THE CYLINDRICAL SURFACE DEFINED BY THE INWARDLY FACING SIDES OF SAID SIDE RODS. 